Fatty acid amides (FAAs) are an emerging family of endogenous signaling lipids implicated in a broad range of physiological processes, including pain, inflammation, and drug addiction. A prototype FAA anandamide serves as an endogenous ligand for the central cannabinoid (CB1) receptor. Although anandamide binds and activates the CB1 receptor in vitro, this FAA induces only weak cannabinoid behavioral effects in vivo due to rapid catabolism. The objective of this proposal is to identify and characterize enzymes that regulate the function of anandamide and other bioactive FAAs in vivo. One candidate enzyme responsible for terminating FAA signals in vivo is fatty acid amide hydrolase (FAAH), which hydrolyzes anandamide and related FAAs in vitro. To test the role that FAAH plays in regulating FAA function in vivo, we have created FAAH-knockout [FAAH(-/-)] mice. FAAH(-/-) mice possess greatly increased endogenous brain levels of anandamide (and other FAAs) and display reduced pain sensation that is reversed by CB1 antagonists. These data indicate that FAAH is a key regulator of FAA signaling in vivo, setting an endocannabinoid (EC) tone that modulates pain perception. More recently, we have devised a transgenic method to restrict the expression of FAAH to specific tissues, allowing us to determine that peripheral FAAs regulate inflammation through a CB receptor-independent mechanism. In this application, we propose to extend our analysis of transgenic FAAH mouse models to examine the role that the EC/FAA system play in multiple forms of acute and chronic inflammatory pain. Additionally, building on our recent discovery of a mutation in the human FAAH gene linked to problem drug use, we will compare the drug dependence and withdrawal responses of FAAH(+/+) and (-/-) mice. Finally, we will create and analyze knockout mice lacking candidate FAA biosynthetic enzymes. These studies will elucidate the functions of key enzymes that regulate FAA signaling in vivo. These proteins may represent new targets for the treatment of pain, addiction, and other neurological disorders.